1. Field of the Invention
The invention relates generally to a device for grinding a spherical end face of a roller-shaped workpiece, and more specifically to a grinding device for grinding a spherical end face of a roller-shaped workpiece, such as a workpiece for a tapered roller of a tapered roller bearing.
2. Description of Related Art
A grinding device 71 for grinding a spherical end face of a roller-shaped workpiece is described in Japanese Patent Application Publication No. 60-6335 (JP 60-6335 A). In the grinding device 71, a roller-shaped workpiece W is held by a disc-shaped carrier 72 horizontally disposed, and retained by an upper rotary retaining member (first rotary retaining member) 73 and a lower rotary retaining member (second rotary retaining member) 74, as shown in FIG. 6 and FIG. 7.
A C-shaped grinding wheel, of which the inner peripheral face (grinding face) is formed along the outer peripheral face of the carrier 72, is used as a grinding wheel 75. A workpiece inlet 76 and a workpiece outlet 77 are arranged at the opening of the C-shaped grinding wheel 75.
The upper rotary retaining member 73 is fixed to an upper rotary drive shaft 78, and rotates at a predetermined speed. The lower rotary retaining member 74 is fixed to a lower rotary drive shaft 79, and rotates at a predetermined speed. The upper rotary drive shaft 78 and the lower rotary drive shaft 79 rotate in the opposite directions. The upper rotary drive shaft 78 applies downward pressure to the upper rotary retaining member 73 with the use of a pressure cylinder (not shown).
As a grinding wheel used in a device for grinding a spherical end face of a roller-shaped workpiece, in addition to the foregoing C-shaped grinding wheel 75, a cup-shaped rotary grinding wheel is also known (Japanese Patent Application Publication No. 2011-152597 (JP 2011-152597 A)).
The conventional grinding device described above is large due to a large outside diameter of the carrier and/or a large outside diameter of the grinding wheel. Therefore, more compact grinding devices have been demanded. In addition, improvement in the machining accuracy of an end face of a roller-shaped workpiece has been demanded.